Kai Province

It lies in central Honshū, west of Tokyo, in a landlocked mountainous region that includes Mount Fuji along its border with modern Shizuoka Prefecture.

Kai was one of the original provinces of Japan established in the Nara period under the Taihō Code.

After Nobunaga’s assassination at the Honnō-ji Incident, the province was contested between Tokugawa Ieyasu and the Go-Hōjō clan based in Odawara.

This caused the triangle conflict between those three factions in the event which dubbed by historians as Tenshō-Jingo War broke out.

Kai Province was entrusted briefly to Tokugawa clan members or the highly trusted Yanagisawa clan from 1705-1724 as Kōfu Domain, but for the most part was retained as tenryō territory ruled directly by the shogunate through a succession of hatamoto-class daikan.

Map of Japanese provinces (1868) with Kai Province highlighted
Hiroshige ukiyo-e "Kai" in "The Famous Scenes of the Sixty States" (六十余州名所図会), depicting the Saruhashi, a bridge in what is now Ōtsuki, Yamanashi .